Blitz Captive Bolt Stunner Loads A centerfire cartridge is a cartridge in which the primer is located in the center of the cartridge case head. Unlike rimfire cartridges, the primer is a separate and replaceable component. Centerfire cartridges are generally larger and capable of higher power loads. These cartridges are more powerful because they can hold higher pressures than similar rimfire cartridges thus they are also more efficient for their size.50 Loads / Package Green – Low for animals 100 lbs or lessYellow – Medium for cows and horsesBlue – Strong for large horses and bullsRed – Power for large bulls